Resnatron filament basket



Dec. 15, 1953 v w. H. KOHL RESNATRON FILAMENT BASKET Filed Sept. 21, 1950 lllllllf a INVENTOR. WALTER H. KOHL BY a ly.

Patented Dec. 15, 1953 UNITED STATES PATENT OFFICE Walter H. Kohl, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application September 21, 1950, Serial No. 186,038

6 Claims.

This invention relates to a resnatron filament basket. 7 v

The electronic device known as a resnatron requires a concentric. filament which gives an unusually large amount of emission. Filament baskets have been used which comprise staples of tungsten that are mounted in holding rings at either end. The end rings are usually liquid cooled. Cooling of the end rings results in' an emission lossfor thereason that heat flows from the hot emitting portion to the rings. This is undesirable. Another problem encountered in the fabrication of resnatron filament baskets is that the emitting portion of the basket tends to bowand become misaligned .because of thermal expansion.

It is an object '01 this invention, therefore, to

provide a resnatron filament basket in which the thermal expansion of the emitting portion! is compensated to prevent misalignment.

Another object of this invention is to provide a hot resnatron filament'basket wherein the por tions of the basket adjacent the emitting part are maintained at a relatively high temperature and, thus, end cooling of the active portion is prevented. I

Still another object of this invention is to provide a resnatron filament basket which may be formed as a unitary structure from the same material which forms the emitting portions.

Still another object of this invention is to provide a composite resnatron filament basketwhich is formed by spinning about a soft low melting point core. 1

, A feature of this inventiojnfis found; in the provision for a resnatron filament basketcoinprising a plurality of center'emitting segments that are integrally formed with a lower and upper end portion. An expansion member is attached to the upper portion and compensates for thermal expansion of the basket.

Further objects, features and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which:

Figure 1 is a perspective view of the resnatron filament basket of this invention;

Figure 2 is a side view showing how the filament basket is spun about a mandrel; and,

Figure 3 is a view showing how the emitting portions are milled into the resnatron filament basket.

Figure 2 illustrates a mandrel In which is formed from metal which has a relatively low melting point. It is mounted on the shaft ll which may be mounted in suitable bearings and connected to a driving means as, for example. a lathe. 'A cylinder l2, of tantalum or tungsten, is mounted axially of the mandrel I0 and a spinning tool I3 is used to form the cylinder I 2 to the shape of the mandrel I0; After one end I4 of the filament basket has been shaped, the opposite end I6 is spun. Figure 3 illustrates the filament basket l2 after it has been spun to theshape of the finished basket. The shaft H is rigidly mounted in a milling machine and a cutting tool I! is used to form a plurality of emitting sections l8 in thebasket. The mandrel I0 is cut by the tool I! and gives a steady backing to the thin cylinder l2 as it is cut.

After the emitting strips [8 have been formed with the cutting tool 11, the cylinder [2 and the mandrel ID are subjected to temperature which is high enough to' melt the mandrel ID. The cylinder l2 which'may be formed of tantalum or tungsten has ahigh melting point, and therefore remains intact as themandrel melts and runs out of the filament basket thus formed. R'Figurel shows the cylinder I 2 with an expansion member mounted therein after it has been freed of the mandrel. A coaxial base member 19 comprises an outer support 2| and an inner support 22. The outer support 2! is formed with fluid passageways 23 through which a cooling fiuid is circulated. The center support 22 is hollow and has a stand pipe 24 mounted therein. I

Coolingfluid is supplied'to the stand pipe 24 and passes out through 'the spaceibetween the members 22-and 24. Mounted to the end of the inner support member 22is a rod 26 which has its upper end connected to adisc 21. The disc 21 may be madeof tantalum or tungsten and has its outer edge 28 welded to a rim 29 formed in the cylinder [2 during the spinning process. A heat shield 3| fits concentrically about the rod 26 and is attached to the disc 21. It extends substantially the entire length of the rod 26.

An adapter 32 is connected to the top end of the outer connector 2| by welding and has its top end welded to the cylinder l2. The member 32 may be made of tantalum or tungsten and has a relatively high melting point. A center open- 1 ing 33 is formed therein to allow the rod 26 to inder 12. From the transitional section 34 the current flows through the emitting portions I8, to a lower transitional portion 36, and to the member 2| through the adapter 32.

The rod 26 is made out of a material such that when thermal expansion occurs in the portions 36,34, and 18 it will expand an equal amount and thus prevent misalignment and buckling of the active sections [8. 'Thezactiveportion l8 of the basket should operate at about 2200 "degrees Kelvin and the heat shield allows the rod 26 to operate at a much lower temperature as, for example, 550 degrees Kelvin. If copper is used for the center rod 26 and it is operated at 550 degrees Kelvin it will expand thesameramount-as the basket wherein the active portions l8=are operating at 2200 degrees Kelvin and the transition members at a lower temperature. as,.for example, 1300 degrees Kelvin. It is to be understood, of course, that the transition members 34 and 36 will have a temperature-gradient from very hot adjacent the active .portions [Bite the coolest portions adjacentthe aends.

It is ,seen'that applicant's invention provides-a resnatron filament basket which is integrally formed by spinning about a=low melting point mandrel, .machining the active portions, and mounting an expansioncenter: post through the basket to compensate for thermal expansion. The results are an improved basket in'which misalignment is greatly" decreased. Another advantage obtained-is that since the transition members and. 36 are made of tantalum ortungsten they need not be liquid cooled and thus the. active portions l8 are not'subjectedx to agreat deal of end cooling. A high degree'of emission is obtained, therefore, over-their entire active lengths. The entire assembly will operate atxa higher temperature and-the'heat shield 3| will preventxthe rod 26 .fromrreaching too high a temperature. The heat shield -3| is made from tantalum or other-materialwhich has a high melting-point so that itdoes not-meltat the highxoperating temperature.

Although this invention has been described with respect to particular embodimentsthereot, it is not to be so limitedas changes and modifications may be made therein :-which :are within the full intended scope .of the invention as tdeflned by expansible member and maintaining them insulated from each other.

3, A resnatron filament basket comprising, a

hollow Chinese-lantern shaped emitter, an exipansible rod extending axially through said emitter-and'with the'one end connected to one end .of said v.emitteiya hollow cylindrical member attached to the upper end of said emitter and extending down ,over said expansible rod, and a base member attached to the bottom end of said emitter and the bottom" end of said center'post.

4, A resnatron filament basket comprising, a lanternsha-ped emitterformed with a plurality of longitudinal slots in the center section thereof, a rim formed about the upper end of said emitter, a disc connected tosaid rim, a rod attached to the center "of said disc and extending axially through said emitter, a heat shield of cylindrical shape attached to said disc and about said rod, a coaxial base member with the center portion connectedsto said rod and .the outer portion connected to the lowerend of said emitter.

5..A resnatron filament basket icomprising, a hollow cylindricalemitter with the central portion formed with a plurality of longitudinal slots, a disc attached to the upper end of said emitter, arod extending axially through said emitter and attachedto said disc,-a'-coaxial base member with its outer portion connected to the bottom end of said emitter, andthe centerportion ofthe base member attached to said rod.

6. Apparatus according to .claim 5 wherein a hollow cylindrical heat shield of a diameter smaller than said emitter is attached 'to said disc with the. rod extending radially therethrough.

WALTER H. KOHL.

References Cited -.in the file of this patent UNITED STATES PATENTS 'Varian Aug. .1, 1950 

